Page:South African Geology - Schwarz - 1912.djvu/207

 outpourings of basalt occur equivalent to the Drakensberg lavas, such as those which form the lip of the Victoria Falls. The following is a list of the formations represented: —

Later! te, tufa Recent. Somabula gravels and Plateau gravels ... Tertiary. Tuli amygdaloid, Botoka basalts Volcanic. Forest sandstone, Samkoto Series = Cave Sandstone. Coal Measure Series (Escarpment grits), _ jldutywa or Matobola and Busse Beds... ... / I Beaufort Series. Waterberg sandstone. Dolomite. f Conglomerate Series with interbedded lavas. 1 Banded Ironstone Series ' I Basement schists with intrusive granite. Basement granite and gneiss.

The Auriferous System is folded in the granite and is intruded by later granite. The basement schists consist of altered basic rocks (epidiorite), hornblende, and chlorite schists, which carry most of the payable quartz reefs. The Banded Ironstone Series is made of magnetite quartzites and ferruginous slates; often on the surface the quartzite is brilliantly white like lump sugar, and the brown iron ore in layers between the white rock gives the whole a striking appearance which miners have emphasized by applying to these ironstones the name of calico rock. The Conglomerate Series is similar to the conglomerates of the Elsberg or Ventersdorp System, and, like them, has volcanic rocks associated with it. It has been found to be auriferous in places, and is hence called a banket, that is, a conglomerate carrying gold. The Witwatersrand banket is made up entirely of quartz or quartzite pebbles, whereas the Rhodesian banket contains pebbles of granite and other rocks. It is of sedimentary origin, but volcanic agglomerates also occur,